When these parties were divorced a separation agreement providing monthly child support was incorporated into the decree. That agreement contained an escalation formula for child support and an example of how the formula was to operate. Both the formula and the example are unmanageably vague, and the two are even inconsistent. The trial court refused to hold the former husband in contempt for nonpayment of increased child support. We find no error in that determination. See Code Ann. 30-220.